Note:
The base *kop- has been associated with a number of words in other Indo-European branches with varying vowels and sometimes with initial s (as Latin cāpō, cāpus "castrated male chicken, capon," Greek skáptein "to dig, cultivate by digging," Old Church Slavic skopiti "to castrate," skopĭcĭ "eunuch"). These forms cannot be accounted for by regular ablaut variation, and if they actually descend from a common ancestor and are not at least partially sound-symbolic, the ancestor is more likely a European substratal word (or words) rather than a true Indo-European base.